Hi. Ive Been Taking Cerazette For Almost A Year And

Hi. Ive been taking cerazette for almost a year and a half and have never had a period on it which i know is normal. But today ive had alot of cramping and brown discharge, theres also been some brown blood clots, quite large ones. I am sexually active on a weekly basis as in a commited relationship. Have not missed any pills. What does this mean?